Cationized PVA as a Sizing Component in Wet Chop Processing

ABSTRACT

The catonized sizes poly vinyl alcohol and hydroxy celluloses are used in the manufacture of wet chop to improve product quality, cut cost and reduce the expenses incurred disposing of whitewater.

FIELD OF THE INVENTION

This invention relates to the processing of organic and inorganic fibers used to reinforce composite materials. More particularly, the invention relates to novel sizing agents applied to natural and man-made fibers prior to being chopped into staple.

BACKGROUND OF THE INVENTION AND PRIOR ART

Non-woven fabrics have certain advantages over woven materials including using less-costly equipment in manufacture, the facile mixing of numerous fibers into a fabric and the ability to incorporate slick fibers such as glass and carbon.

After man made fibers are spun, the mass of fibers is treated with a size to lubricate the fibers for protection against rubbing before and after chopping of the long strand bundles to form staple. This wet chop, typically kept in closed containers or plastic bags, is ultimately dumped into large tanks for dispersion. The tanks contain whitewater, a mixture of water and a variety of agents including viscosity modifiers and defoaming agents. Polyacrylamide (PAM)-based whitewaters are common in the industry. The sizing of the wet chop is critical to good dispersion in the whitewater.

Once the fibers have been dispersed evenly, the slurry is introduced to a Fourdrinier or other web type sheet former device. The fibers are treated with a binder such as acrylate or phenol formaldehyde and dried. Ideally, residual sizing on the fibers helps with the coating by binder.

Sizing used on wet chop, especially wet chop fiberglass, is typically non-ionic materials such as polyvinyl alcohol (PVA) and hydroxymethyl cellulose which is quite soluble in whitewater and buildup in whitewater as it is recycled. As a result, whitewater must be treated to remove sizing or disposed of as a regulated waste since the additives are not biodegradable and raise BOD in waters.

Cationic polyvinyl alcohol compositions which are graft copolymers in methyl chloride quaternary salt form or methyl sulfate quaternary salt form are taught for use as wet end additives in the papermaking process in conjunction with a separate sizing agent in U.S. Pat. No. 7,144,946.

A polyol in conjunction with a cationic lubricant (alkyl imidazoline) a water dispersible amide is taught as a sizing for glass fiber stands in U.S. Pat. No. 4,465,500.

There remains an unmet need for a wet chop sizing which is inexpensive, effective for the protection of wet chop and dispersion in whitewater while remaining on the fiber during further processing.

BRIEF DESCRIPTION OF THE INVENTION

A cationized polyvinyl alcohol or hydroxyl methyl cellulose is the form of a quaternized ammonium compound or is provided as a sizing for spun organic and inorganic fibers.

DETAILED DESCRIPTION OF THE INVENTION

Poly vinyl alcohols having an average molecular weight between 13,000 and 100,000, preferably between 13,000 and 500,000 are preferred. A degree of hydrolysis of 70 to 99%, preferably 72-89%. A quaternized salt is prepared by reacting a polyvinyl alcohol with a quaternary salt of a dialkylamino ethyl acrylate in the presence of a catalyst such as a persulfate or peroxide. Preferred salts are chloride and sulfate. Ammonium persulfate is the preferred catalyst.

The effective molecular weight of PVA can be raised significantly by the addition of borate ions due to extensive cross-linking. Borated PVA are preferred embodiments of this invention.

Hydroxy cellulose, especially carbon methyl cellulose are also cross- linked by borate which can be used to adjust effective molecular weights and viscosity. Mixtures of cationized PVA and hydroxyl celluloses are included within the scope of the invention. Specific amounts used depend upon the ratio of alcohol precursors and their relative molecular weights.

The cationized PVA may be produced as an aqueous suspension which is adjusted to a water content of 20%-80% by weight.

The cationized PVA improves dispersion of fibers when wet chop is added to whitewater due to polar nature of the sized fibers. The low degree of dissolution into whitewater improves wet tack of the fibers on the wet web and allows increased processing speed. The polarity of the cationized size reduces the need for biocides in the whitewater. The lower solubility in whitewater reduces the number of changes of whitewater required and reduces the BOD of the waste whitewater.

The invention has been described in terms of examples which demonstrate the utility but do not limit the scope of the invention. Changes or additions apparent to one with skill in the art are within the scope and spirit of the invention. [need paragraph of hydroxyl cellulose, CME].

INDUSTRIAL UTILITY

The use of cationized polyvinyl alcohol as a sizing agent for wet chop improves performance and lowers production costs for products made using fiber, non-woven fabrics as a basis for construction. Construction materials such as shingles and roll goods are exemplary. 

1. A sizing composition for natural and synthetic polymer fibers comprising an aqueous solution of a cationized alcohol.
 2. A sizing composition according to claim 1 which is a cationized polyvinyl alcohol having an average molecular weight of 13,000 to 100,000.
 3. A sizing composition according to claim 2 wherein said cationized polyvinyl alcohol has an average molecular weight of 13,000 to 50,000.
 4. A sizing composition according to claim 2 having a degree of hydrolysis of between 70 and 99%.
 5. A sizing composition according to claim 4 having a degree of hydrolysis of between 72 and 89%.
 6. A sizing composition according to claims 2 which is a borated polyvinyl alcohol.
 5. A sizing composition according to claim 1 wherein the cationized alcohol is a cationized hydroxyl cellulose.
 6. A sizing composition according to claim 1 which is a quaternized salt.
 7. A sizing composition according to claim 1 which is applied in the manufacture of wet chop. 